markz528 the 91-xx series are the whole blade looks like. They can be bought for sure. The blade is fine as long as the refill in it is 3/8" wide. Are the 91-18s you bought 3/8" wide?

‘72 Charger, 5.9 Magnum, Tremec 5 spd., Pro-Touring
‘14 Big Horn, Quad Cab, 4x4, 1500